Arrangement for removing particles of dust from the work zones of pneumatic,eroding-type work tools



y 6, 1969 N. OSTEN ASTROM 3,442,337

ICLES OF DUST FROM THE WORK ZONES ARRANGEMENT FOR REMOVING PART OF PNEUMATIC, ERODING-TYPE WORK TOOLS Filed Oct. 21, 1966 United States Patent 3 442,337 ARRANGEMENT FOR REMOVING PARTICLES OF DUST FROM THE WORK ZONES OF PNEU- MATI C, ERODING-TYPE WORK TOOLS Nils Osten Astriim, Barrstigen 25, Bromma, Sweden Filed Oct. 21, 1966, Ser. No. 588,418 Claims priority, application Sweden, Oct. 25, 1965, 13,734/ 65 Int. Cl. E21c 7/00; E21b 21/00; Bd 17/14 US. Cl. 173-61 4 Claims ABSTRACT OF THE DISCLOSURE Apparatus for removing dust and the like from the working zone of a pneumatic tool in which exhaust air from the tool is coupled with a vacuum source to obtain a synergistic effect in the dust removal force. The improvement more particularly comprises the application of an auxiliary source of vacuum connected downstream of the main vacuum source in a common dust exhaust conduit to create a partial vacuum downstream of said main vacuum source, thereby increasing the effect of said main evacuation source upstream thereof.

The present invention relates to an arrangement for removing, by suction, particles of dust from areas in which pneumatitc, eroding-type work tools, such as drills, grinding machines, pneumatic chisels and the like are working, said tools being of the type which presents a dust outlet conduit leading from said working zone to a dust collecting station, the outlet air from the tool being used by passing said air into the dust outlet conduit substantially in a direction toward the dust collecting station as a carrier for carrying away the dust.

In the case of rock-drilling machines, it has previously been suggested in order to fulfill this purpose that particles of dust injurious to health be transported away from the work zone by allowing the outlet air of the pneumaticdrilling machine to flow freely into a dust outlet conduit, which passes from the work zone to a dust collecting station. Experiments, however, have shown that the amount of dust lead away by these means is insufficient to eliminate the health risks.

An artisan may possibly realize that the deficiency in the effectiveness of the known devices is due to insufficient flow velocity and that consequently the solution to the problem lies in increasing the pressure of the propelling outlet air from the tool. Closer thought, however, would reveal that this solution is not realistic. Increase in pressure would increase the amount of air per unit of time and thus give rise to stronger turbulence and consequently not only an increased spreading of dust but also at the same time to increased wear in the walls of the conduit. Furthermore, it would be necessary to re-design the pressure tool.

A closer study of the phenomenon has shown that not only the fiow velocity but also, at the same time, the density of the carrying and transporting air is of a decisive significance for a correct functioning of the apparatus. The object of the present invention is therefore to provide an arrangement in which the exhaust air of the working apparatus is passed into a duct exhaust conduit through an ejector means for the purpose of creating a partial vacuum upstream of the ejector means to suck away effectively the particles of dust from the working site, and is mainly characterized by the fact that an auxiliary air evacuation source in the form of a fan or another ejector is connected to the dust exhaust conduit downstream of said ejector means, thereby creating a partial vacuum downstream of the air inlet.

3,442,337 Patented May 6, 1969 ICC The exhaust air inlet is thus suitably designed so that, for instance, by means of some form of constriction, the said air is given an increased velocity on entrance into the exhaust conduit.

The invention will be more closely described with reference to an example of the same shown diagrammatically on the accompanying drawing, and in conjunction therewith additional characteristics of the invention will be disclosed.

In the drawing:

FIGURE 1 is a side-view, partly in section, of a pneumatic chisel provided with an arrangement according to the invention,

FIGURE 2 shows diagrammatically a pneumatic work tool, the air-exhaust of which is connected to a dust outlet conduit leading to a dynamic dust separator; and

FIGURE 3 shows in longitudinal section an ejector arrangement intended to replace the holes shown in FIG- URE 1, in an alternative embodiment.

The reference numeral 1 in FIG. 1 indicates the tool proper, to which is connected a compressed air hose 2 or the like. Further, the upper portion of the tool is encased by a collecting chamber 3 intended to receive exhaust air coming from the apparatus (not shown) which drives the tool 1. A tube 5, the bottom of which is open, is passed from the work zone 4 of the tool and continues into a tubular portion 6 which, in turn, communicates via a coupling 7 with a hose 8 or the like enclosing the compressed air conduit 2. The portion of the tube 6 which ex tends through the chamber 3 is provided with holes 9 directed towards the hose 8, wherein the holes may have the form of constrictions or be replaced by ejector nozzles.

Furthermore, it may be mentioned that although not shown in FIG. 1 of the drawing, the hose or conduit 8 is connected at some suitable position, preferably at its remote end, to a separate air evacuation source which tends to alleviate the air counter-pressure, seen in the fiow direction, in front of holes 9. Any type of evacuation means suitable for the purpose may be used such as, for instance, a fan.

When the device is operating, the exhaust air flows out from the chamber 3 through holes 9 or the like at an increased velocity, firstly due to the throttling effect and secondly owing to the sub-pressure in the exhaust conduit in front of said holes, caused by the fan. By reason of the special direction of the holes towards the separate subpressure source, a strong fiow through the entire dust exhaust conduit, represented by tubes 5, 6, coupling 7 and hose 8, is obtained. Furthermore, reduction of the impact effect at the holes, restrictions or ejector means is prevented.

To illustrate more clearly the principle of construction of an arrangement according to the invention, for re moving dust from the working zone of a machine tool, reference is made to FIGURE 2, where the reference numeral 10 indicates a pneumatic drill provided with a compressed-air inlet 11 and an ejector housing 12, fitted with an ejector nozzle. The ejector nozzle is fed with the exhaust air from the machine tool and at the same time serves as a through-flow channel for dust laden air sucked from the working zone 13, through the intermediary, among other things, of the ejector effect of the exhaust air. Further, a hose 14 or the like, of relatively unlimited length, passes to a dynamic dust separator, indicated generally by the reference numeral 15. The dust separator 15 is connected by means of a conduit 16 to a source of sub-pressure which acts, via the dust separator, in the dust outlet conduit 14 according to the above discussed principle of the invention. The dust separator 15 is also provided, at its bottom portion, with an outlet 17 for the separated dust, which can be removed at intervals in the direction of arrow A.

The sub-pressure source is represented in FIGURE 2, 3y way of an example, by a diagrammatically illustrated :jector means 18, driven by compressed-air which is passed ;hrough a conduit 19.

As described in the foregoing, in FIGURE 1 the exiaust air from the machine tool is permitted to flow, via the chamber 3, through the holes 9, which face the source of sub-pressure, into the dust outlet conduit. It has, however, been shown that the efiiciency of such an arrangement can be still further improved, with respect to its suction-removal capabilities, by arranging an ejector in place of the holes 9. An example of this is shown in FIGURE 3 Where the reference numeral 20 indicates a connection for the exhaust air flowing from the tool. This connection communicates directly with a pressure-equalizing chamber 22, concentric with the ejector nozzle 21, the air being able to pass through a gap 23 between the nozzle 21 and a constricting portion 24, and continuing in the direction of arrow B towards the source of sub-pressure. It should also be mentioned that the nozzle 21 communicates, via a channel 25, with the working zone of the tool, as in FIG- URES 1 and 2, where from dust laden air is sucked up in the direction of arrow C.

In addition to the invention advantageously eliminating the disadvantages linked with the treatment of dust in this respect an essential reduction of deleterious noise is also obtained, as an extra unexpected effect, in spite of the substantial velocities of the air.

The invention is not restricted to the illustrated and described examples of the same but can be varied within the scope of the following claims.

What is claimed is:

1. An arrangement for removing, by suction, particles of dust from the work zone of a pneumatic, eroding-type work tool, said arrangement comprising a dust exhaust conduit leading from said work zone to a collecting station for the dust, ejector means by which exhaust air from the tool is used as a carrier for transporting away the dust and is led into the dust exhaust conduit in a direction generally towards the dust collecting station, and an additional vacuum source, the dust exhaust conduit being connected to said vacuum source at said collecting station to lower the air pressure in the dust exhaust conduit downstream of the ejector means.

2. An arrangement as claimed in claim 1, wherein the ejector means has an exhaust inlet into said dust conduit which has a shape such that the exhaust air receives an increased velocity on entering the exhaust conduit.

3. An arrangement as claimed in claim 2, wherein the inlet is a constriction.

4. An arrangement as claimed in claim 1 comprising a compressed air conduit leading to the tool enclosed by the dust exhaust conduit.

References Cited UNITED STATES PATENTS 981,409 1/1911 Goodspeed 173-61 X 1,223,027 4/1917 Brackett 175-213 X 1,981,570 11/1934 'Price 175-213 X 1,985,157 12/1934 Friedman 175-213 X 3,144,912 8/1964 Boehm 175-213 3,351,143 11/1967 Seibold 175-213 X NILE C. BYERS, JR., Primary Examiner.

' US. Cl. X.R. 175-213 

